I am not sure of this, but I don't think its only one female and several males. I think its several of both sexes.
I would have less males in a tank than females, as the males are aggressive breeders. I have three females and two males in the same tank.
I don't know if actual mating balls have been achieved in captivity? Maybe. But not that I have seen/heard.
I think that the females are the main problem with captive breeding this species ( just my opinion ). They don't seem to want to breed, whereas the males will amplex everything ( intake filter tubes, fish, other species! ). So I think that if wanted to accomplish this you would have to either have a basement that fluctuates with the season or have the tank outside. So that the females might feel more "wild" and be enticed to breed more easily. Just my thoughts.
I don't know weather or not it is unhealthy for the female, but as long as she can get air I don't think it would be unhealthy.
Hope this helps Erik! -Seth